1. Field of the Invention
This invention generally relates to a one-way clutch assembly, and, in particular, to a sprag-synchronized one-way clutch assembly. More specifically, the present invention relates to a retainer for retaining a plurality of sprags in position in a sprag-synchronized one-way clutch assembly.
2. Description of the Prior Art
A sprag-synchronized one-way clutch assembly is well known in the art. In such a clutch assembly, a plurality of sprags having a predetermined cross sectional shape are arranged in an annular space defined between an inner ring and an outer ring, whereby the sprags are set constrained between the inner and outer rings to prevent a relative rotational motion between the inner and outer rings to thereby allow to transmit a rotational force between the inner and outer rings when the inner ring tends to rotate in a first direction relative to the outer ring; whereas, the sprags are set unconstrained between the inner and outer rings to thereby allow a relative rotational motion between the inner and outer rings when the inner ring tends to rotate in a second direction, which is opposite to the first direction, relative to the outer ring.
FIGS. 12 and 13 illustrate a typical prior art double retainer sprag-synchronized one-way clutch assembly of the above-described type. The illustrated clutch assembly includes a pair of inner and outer sprag retainers for retaining the sprags in position and insuring that the sprags move or rotate in unison during operation. As shown, the one-way clutch assembly shown in FIGS. 12 and 13 includes an inner ring 1 and an outer ring 2 between which an annular space is defined for receiving therein a plurality of sprags 3 having a cross sectional shape similar to a gourd or the figure of "8" as spaced apart from each other. The sprags 3 are maintained in position by a pair of inner and outer sprag retainers 4 and 5 so that the sprags 3 are equally spaced apart from one another circumferentially along the annular space defined between the inner and outer rings 1 and 2. Also provided between the inner and outer sprag retainers 4 and 5 is a ribbon spring 6 which normally urges the sprags 3 to be in contact with the inner and outer rings 1 and 2. In such a double retainer type sprag-synchronized one-way clutch assembly, the sprags 3, the inner sprag retainer 4, the outer sprag retainer 5 and the ribbon spring 6 define an integrated unit so that they would not fall apart even before they are assembled into the annular space between the inner and outer rings 1 and 2.
Drag clips 7 are normally attached to the outer sprag retainer 5 so as to hold the outer sprag retainer in a fixed relation with the outer ring 2 due to the spring action of the drag clips 7. Drag strips 8 are normally provided with its both ends attached to the inner sprag retainer 4, and each of the drag strips 8 has its central portion resiliently pressed against and in sliding contact with the inner ring 1. These drag clips 7 and drag strips 8 serve to positively operate the sprags 3 to thereby secure an engagement between the sprags 3 and each of the inner and outer rings 1 and 2 during transmission of torque between the inner and outer rings 1 and 2 and also to minimize the wear of the sprags 3 during an idle state in which no torque is transmitted between the inner and outer rings 1 and 2.
As described above, a sprag-synchronized one-way clutch assembly typically includes a ring-shaped sprag retainer 50 as shown in FIG. 10. The sprag retainer 50 includes a ring-shaped thin metal plate 51 formed with a plurality of pockets 52, each for retaining therein a corresponding sprag 3, as spaced apart from one another at a predetermined pitch in a circumferential direction. Such pockets 52 are typically formed by punching or blanking and thus the pockets 52 are typically formed one at a time. The sprag retainer 50 is also formed with a flange or raised lip portion 53 at one rim of the ring-shaped plate 51.
In order to provide such a sprag-synchronized one-way clutch assembly light in weight, it has been proposed to use a plastic material for some elements of the clutch assembly. For example, U.S. Pat. No. 4,327,822, issued to Vogele et al. on May 4, 1982, teaches to fabricate a cage 8 from a plastic material, but the cage 8 has a structure which is open at one side as shown in FIG. 6 of that patent. However, if it were tried to fabricate the prior art sprag retainer 50 shown in FIG. 10 from a plastic material, difficulty would be encountered, especially in forming pockets 52 of the sprag retainer 50. In addition, the prior art sprag retainer 50 shown in FIG. 10 hereof can be fabricated only one at a time and it is almost impossible to fabricate the retainer 50 in mass production. If the sprag retainer 50 shown in FIG. 10 were fabricated using a plastic material, there would be formed discontinuous merging points A of flows of plastic material at junctions between circumferential portions and axial portions of the retainer 50 as shown in FIG. 11. These merging points A define local weak spots having reduced rigidity as compared with the remaining portion of the retainer 50. In addition, since the prior art sprag retainer 50 is in the shape of a ring, its flexibility or elastic deformability is limited so that the sprag retainer 50 could be permanently damaged once a concentrated force were applied locally. U.S. Pat. No. 4,494,636, issued to Wakabayashi et al. on Jan. 22, 1985, teaches a serpentine-shaped retainer 9 for use in a one-way clutch as shown in FIGS. 10 and 11; however, the retainer 9 of this patent is fabricated from a rod having a circular cross section by bending the rod alternately and joining the ends together